Noise reduction made of rubberized bituminous top layer report

1
A Technical
Seminar Report
On
NOISE REDUCTION IN PAVEMENT MADE OF
RUBBERIZED BITUMINOUS TOP LAYER
Submitted in partial fulfillment of the requirement
For the award of the degree of
BACHELOR OF TECHNOLOGY
IN
CIVIL ENGINEERING
By
ABDUL AZIZ 13QH1A0101
Under the esteemed guidance of
K. VENKAT
Assistant professor
Department of Civil Engineering
HOLY MARY INSTITUTE OF TECHNOLOGY AND SCIENCES
(Approved by AICTE New Delhi, Affiliated to JNTU Hyderabad, Telangana)
BOGARAM (V), KEESARA (M), R.R DISTRICT-501301.
2013-2017

2
Holy Trinity Educational Society
(College of Engineering)
Approved by AICTE New Delhi, Affiliated to JNTU Hyderabad, Telangana.
_____________________________________________________________________________________
DEPARTMENT OF CIVIL ENGINEERING
CERTIFICATE
This is to certify that the technical seminar report bearing title “NOISE
REDUCTION IN PAVEMENT MADE OFRUBBERIZED BITUMINOUS
TOP LAYER” that is being submitted by the following students in partial fulfillment for the
requirement of award of degree in BACHELOR OF TECHNOLOGY under Civil Engineering
Department from Jawaharlal Nehru Technological University Hyderabad, Telangana is a
record of Boniface work carried out during the academic year 2016-2017.
This is the result of the original work and contribution
Under the supervision of
Mrs. M. SHIVA PARVATHI
Head of the Department
______________________________________________________________________________
Address: Bogaram (V), Keesara (M), Ranga Reddy (D), Telangana, INDIA. PIN 501 301
Phones: 0841-200488, 200499, 040-2335 3909 Mobile: 98488 89962/65,
99484 37912, 9848511063 Fax: 040-2381310
Mail ID: principalhitscoe@gmail.com Website: www.hits.ac.in

3
Holy Trinity Educational Society
(College of Engineering)
Approved by AICTE, New Delhi and affiliated to JNTU, Hyderabad, Telangana.
DEPARTMENT OF CIVIL ENGINEERING
CERTIFICATE
This is to certify that the project work titled “NOISE REDUCTION IN
PAVEMENT MADE OFRUBBERIZED BITUMINOUS TOP LAYER’’ of that
is being submitted by the following students in partial fulfillment for the requirement of award of
degree in BACHELOR OF TECHNOLOGY under Civil Engineering Department from
Jawaharlal Nehru Technology University Hyderabad, Telangana is a record of bonafide work
carried out during the academic year 2016-2017.
This is the result of the original work and contribution
Internal Guidance of
K. VENKAT
Assistant Professor
______________________________________________________________________________
Address: Bogaram (V), Keesara (M), Ranga Reddy (D), Telangana, INDIA. PIN 501 301
Phones: 0841-200488, 200499, 040-2335 3909 Mobile: 98488 89962/65,
99484 37912, 9848511063 Fax: 040-2381310
Mail ID: principalhitscoe@gmail.com Website: www.hits.ac.in

4
ACKNOWLEDGEMENT
With great pleasure I want to take this opportunity to express my heart full gratitude to all
the people who helped in making this technical seminar report in a grand success.
I express my deep sense of gratitude to our internal guide Mr. K. VENKAT, Assistant
professor for his constant guidance throughout our project work.
I would like to thank Mrs. M. SHIVA PARVATHI, Head of Department of civil
engineering, for being moral support throughout the period of my study in HITS COE.
First of all I am highly indebted to Dr. N. SUBHASH CHANDRA, Principal for giving
me the permission to carry out the project.
I would like to thank the teaching and non teaching staff of CE Department for sharing
their knowledge with us.
Last but not least I express my sincere thanks to our Mr. A. VARA PRASAD REDDY,
Chairman, Mr. A. SIDDARTHA REDDY, Vice chairman, Mrs. A. VIJAYA SHARADHA
REDDY, Secretary of HOLY MARY GROUP OF INSTITUTIONS for their continuous care
towards our achievements.
ABDUL AZIZ
(13QH1A0101)

5
CONTENT PAGE NO.
 BSTRACT 5
 INTRODUCTION 6
 LITURATURE RIVIEW 6
 METHODOLOGY 16
 DESIGN AND ANALYSIS 13 
 CONCLUSION 11
 REFERENCES 10


6
LIST OF FIGURE
Sl.NO DESCRIPTION PAGE NO
1 CHARACTERISTICS OF BINDER 1
2 PILOT PROJECT OF VASILIKON STREET 2
3 REMOVAL OF THE OLD SURFACE 3
4 FLEXIBLE PAVEMENT STRUCTURE 4
5 DENSE GRADED HMA 5
6 OPEN GRADED HMA 6
7 STONE MATRIX ASPHALT 6
8 COMPARISONS BETWEEN SMA AND HMA 7
9 MAJOR COMPONENTS OF SMA MIXTURE 7
10 SMA AGGREGATE SKELETON 7

7
ABSTRACT
In Greece more than 60,000 tn End of Life Tires are stockpiled every year often uncontrollable,
causing severe environmental and other socio-economic negative impacts. Studies up to date are
focused mainly on mechanical and physical characteristics of rubberized mixtures (based on
cement, asphalt or soil) in which tire rubber is used either as alternative to natural aggregates or
as additive. However, effect of tire rubber on noise reduction in rubberized bituminous layers,
which is the main topic of present paper, has not been widely studied. In particular, this research
paper is dealing with a sustainable use of tire rubber in asphalt pavement, leading to its generated
noise reduction. An experimental pilot application has been conducted in the frame of a
European Research Project, which has been implemented in a heavy traffic road section, cited
outside Lamia city of Greece, (Vasilikon Street). The upper surface layer of the pavement has
been made of rubberized bituminous mixture, produced by the wet process. Rheological
characteristics of rubberized bitumen as well as basic properties of the implemented, rubberized
bituminous mixture are presented.
Moreover, measurements of noise level, deriving from vehicles’ motion, under
operational conditions took place at the road section right after its implementation as well as
after 8 months of its operation, while all data are presented in details. Results of the
measurements on conventional and modified pavement sections are compared, certifying that
rubberized asphalt layers can be not only environmentally friendly—since a category of solid
wastes (worn automobile tires).
This research has been realized with the contribution of the LIFE financial instrument of
the European Union. Special thanks to the staffs of Municipality of Lamia and of the
Laboratory of Materials Testing and Quality Control of Public Works. The excessive use of
synthetics has led to environmental pollution. This ecological crisis has necessitated the use of
bio-renewable resources and plant fibers. Resources in terms of materials consumed for
construction and maintenance of roads are very scarce and limited. Therefore, there is an urgent
need to identify new technologies that can work well with alternative resources such as agro
based materials and renewal of existing resources without affecting the performance. Some
limited studies have been reported on the use of natural fibers and waste materials in rubber
bituminous top layer.
KEYWORDS: End of Life-Tires, Rubberized Bituminous Mixtures, Noise, Pavement, Traffic,
Waste Management, Noise Controlled by Rubberized Bituminous Layer, Smooth Traffic system.
Internal Guidance- Submitted By-
K. VANKET ABDUL AZIZ
Asst. Professor (13QH1A0101)

8
INTRODUCTION
Annually, a steady stream of large volume of waste tires is generated due to the continual
increase in the number of all kinds of transport vehicles. Especially for the European Community
(Austria, Belgium, Denmark, Finland, France, Germany, Greece, Holland, Ireland, Italy,
Luxembourg, Portugal, Spain, Sweden, UK), this amount is estimated at up to 250 million waste
tires, while equal amounts are estimated for East Europe, North and Latin America, Japan and
Middle-East. In addition to this, 3 billion of EOL Tires have already been stockpiled or land
filled inside the EC and almost 1 billion in North America. In Greece, the annual deposit of
worn mobile tires comes up to 58,500 - 70,000 t, causing a major environmental problem.
Because of the increase in the number of tires accumulating around the world and
environmental hazards associated with them, more nations are looking for ways to make use
of this waste product. Tire rubber can be used in various civil engineering applications, such as
for the production of pastes, mortars and concrete based on cement, based on bituminous binder
or soil. Studies so far, show that utilization of recycled rubber from worn mobile tires in the road
construction sector can be a very promising and environmentally friendly way to eliminate the
nations’ stock of scrap tires.
Rubberized asphalt is a process of incorporating fine crumb rubber particles with
asphalt paving materials. The processes of applying crumb rubber from tire waste in bituminous
mixtures can be divided into two categories: the dry process and the wet process. In the dry
process, crumb rubber is added to the aggregates before introducing the asphalt binder to the
mixture, i.e. crumb rubber acts as a partial replacement to some of the aggregate sizes.
In the wet process, bituminous binder is pre-blended with tire rubber at high
temperature (150˚C -210˚C) and under specific blending conditions. Crumb rubber particles in
the dry process are normally coarser than those in the wet one because they are considered as
part of the aggregate gradations. Whereas, in wet process, fine crumb rubber powders fully react
with bituminous binders and improve the binder properties.
In Greece, the use of rubber in asphalt pavements is still a nationally relatively
unexplored area with many— according to worldwide literature—advantages. This “new”
product remains under-utilized mostly due to lack of knowledge of the technical world.
Rubberized asphalt provides a safer, smoother and quieter road surface. The main theme
of this paper is the effectiveness of rubberized asphalt as traffic noise mitigation measure. In the
frame of life project with Acron ymroadtire (integration of end-of-life tires in the life cycle of
road construction), co-funded by the European Commission, a pilot project of the design and
construction of rubberized asphalt pavement has been conducted, after extensive laboratory
research.

9
A road section in the city of Lamia in the region of Sterea El- lada-Vasilikon street, was
selected for the pilot application. The upper bituminous layer of the pavement has been made
of rubberized bituminous mixture produced by the wet process and its basic properties are
presented. However, present paper focuses on data concerning traffic noise level during various
time periods of a day and theirs’ comparison on conventional pavements and rubberized one of
Vasilikon street, which is characterized by heavy traffic.
India being the second largest growing economy in the world, in par with other
developmental activities, road infrastructure is developing at a very fast rate. Large scale road
infrastructure developmental projects like National Highway Development Project (NHDP) and
Pradhan Manthri Gram Sadak Yojna (PMGSY) are in progress. The spurt in the growth of traffic
and overloading of vehicles decreases the life span of roads laid with conventional bituminous
mixes.
This also leads to the reduction in the riding quality resulting in exorbitant vehicle
operating costs and frequent maintenance interventions due to premature failure of pavements.
Providing durable roads has always been a problem for a country like India with varied climate,
terrain condition, rainfall intensities and soil characteristics.
A good amount of research is going on all over the country in this field to solve the
problems associated with pavements. It is observed that Stone Matrix Asphalt mixture is an ideal
mixture for long lasting Indian Highways. The literature pertaining to the bituminous mixtures is
reviewed in here with a detailed discussion of the noise reduction made from rubberized
bituminous mixtures for top and smooth layer.
Pavements of top layer from rubberized bituminous are called "flexible" since the total
pavement structure "bends" or "deflects" due to traffic loads. This pavement structure generally
composed of several layers of materials which can accommodate this "flexing". In this type of
pavements, material layers are usually arranged in the order of descending load bearing capacity
with the highest load bearing capacity material (and most expensive) on the top and the lowest
load bearing capacity material (and least expensive) on the bottom.
The surface course is the stiffest and contributes the most to the pavement strength. The
underlying layers are less stiff but are still important to pavement strength as well as drainage
and frost protection. A typical flexible pavement structure consists of surface course, base course
and sub base course (optional).
The surface course is the top layer in contact with traffic loads. This layer provides the
characteristics such as friction, smoothness, noise control, rut resistance and drainage. In
addition, it serves to prevent the entrance of excess quantities of surface water into the
underlying base, sub base and sub grade courses (NAPA, 2001). The topmost layer of the surface
course which is in direct contact with traffic loads is the wearing course. This can be removed
and replaced as and when it becomes damaged or worn out. The wearing course can be

10
rehabilitated before distress propagates into the underlying intermediate / binder course. This
layer which constitutes the major portion of the surface course is meant to distribute the load
coming over it. The base course is the layer directly below the surface course which helps in
transmitting the load to the sub grade and generally consists of aggregate either stabilized or
unstabilized. Bituminous mixes like Hot Mix Asphalt can also serve as a base course.
Under the base course layer, a layer of less expensive / inferior quality material can be
provided as sub base course material over the sub grade. The sub base course is optional in many
cases.
The history of the use of fibers can be traced back to a 4000 year old arch in China
constructed with a clay earth mixed with fibers or the Great Wall built 2000 years ago (Hongu
and Philips,1990). However, the modern developments of fiber reinforcement started in the early
1960s (Mahrez, 2003). Zube (1956) published the earliest known study on the reinforcement of
bituminous mixtures. This study evaluated various types of wire mesh placed under an overlay in
an attempt to prevent reflection cracking.
The study concluded that all types of wire reinforcement prevented or greatly delayed the
formation of longitudinal cracks. Zube suggests that the use of wire reinforcement would allow
the thickness of overlays to be decreased while achieving the same performance. No problem
was observed with steel and bituminous mixture compatibility.
Bituminous waste materials are added as reinforcement in bituminous mixtures.
Reinforcement consists of incorporating certain materials with some desired properties within
other material which lack those properties (Maurer and Gerald, 1989). Fundamentally, the
principal functions of fibers as reinforcing materials are to provide additional tensile strength in
the resulting composite and to increase strain energy absorption of the bituminous mixtures.
Some fibers have high tensile strength relative to bituminous mixtures, thus it was found
that fibers have the potential to improve the cohesive and tensile strength of mixes. They are
believed to impart physical changes to bituminous mixtures. Research and experience have
shown that fibers tend to perform better than polymers in reducing the drain down of bituminous
concrete mixtures that is why fibres are mostly recommended (Hassan et al., 2005). Because of
the inherent compatibility of fibres with bitumen and its excellent mechanical properties, adding
fibres to bitumen enhances material strength and fatigue characteristics while at the same time
increasing ductility.
According to Maurer and Gerald fibre reinforcement is used as a crack barrier rather than
as a reinforcing element whose function is to carry the tensile loads as well as to prevent the
formation and propagation of cracks. Finely divided fibres also provide a high surface area per
unit weight and behave much like filler materials. Fibres also tend to bulk the bitumen, so it will
not run off from the aggregates during construction. In terms of efficiency, mixtures with fibre

11
showed a slight increase in the optimum binder content compared to the control mix. In this way,
adding fibres to bitumen is very similar to the addition of very fine aggregates to it. Thus, fibre
can stabilize bitumen to prevent leakage. It is important to know that the appropriate quantity of
bitumen needed to coat the fibres depend on the absorption rate and the surface area of the fibres.
It also depends on the concentration and type of fibres.
If the fibres are too long, it may create the so called ‘‘balling” problem, i.e., some of the
fibres may lump together, and the fibres may not blend well with the bitumen. In the same way,
too short fibres may not provide any reinforcing effect. They may just serve as expensive filler in
the mix.
Fundamentally, fibre improves the different properties of the resulting mix. It changes the
viscoelasticity of the modified bitumen, increases dynamic modulus moisture susceptibility,
creep compliance, rutting resistance and freeze– thaw resistance (Echols, 1989), while reducing
the reflective cracking of bituminous mixtures and pavements (Echols, 1989; Tapkın et al., 2009,
Maurer and Malasheskie,1989). Goel and Das (2004) reported that fibre-reinforced materials
develop good resistance to ageing, fatigue cracking, moisture damage, bleeding and reflection
cracking.
Serfass and Samanos (1996) examined the effects of fibre-modified bitumen on
bituminous mixtures utilizing asbestos, rock wool, glass wool and cellulose fibres The tests
conducted included resilient modulus, indirect tensile strength, rutting resistance and fatigue
resistance. Three studies were performed on a test track in Nantes, France.
The first study showed that, fibre modified mixtures maintained the highest percentage of
voids with a 13 metric ton axle load for 1.1 million times, compared with unmodified and the
other two elastomer modified mixtures. The authors concluded that the decreased susceptibility
to moisture related distress in the porous mixtures tested is due to better drainage. In the second
study, two million load applications were applied to fibre-modified bituminous mixture which
was used as an overlay on pavements with signs of fatigue distress.
After the load applications, the pavement surface was noted to have a well maintained
macrostructure, and practically no cracking. Fibre modified overlays were also constructed over
fatigued pavements in the third study reported by them. After 1.2 million load applications, it
was observed that all of the fibre modified overlays showed no sign of fatigue related distresses
or rutting compared to the unmodified samples which showed signs of distress.
This was in agreement with the findings of the second study, establishing that the fatigue
life of the fibre modified pavement is improved over unmodified mixtures. Fibre modification
also allowed for an increase in film thickness, resulting in less ageing and improved binder
characteristics. Addition of fibres also resulted in the reduction of temperature susceptibility of
bituminous mixtures.

12
Simpson et al. (1994) conducted a research on modified bituminous mixtures using
polypropylene, polyester fibres and polymers. Two blends of modified binder were evaluated.
An unmodified mixture was used as a control sample. Mixtures containing polypropylene fibres
were found to have higher tensile strength and resistance to cracking than the others.
Studies by Brown et al. (1990), showed that some fibres have high tensile strength relative to
bituminous mixtures, thus it was found that fibres have the potential to improve the cohesive and
tensile strength of bituminous mixes. They are believed to impart physical changes to
bituminous mixtures by the phenomena of reinforcement and toughening.
This high tensile strength may increase the amount of strain energy that can be absorbed
during the fatigue and fracture process of the mix. Finely divided fibres provide a high surface
area per unit weight and behave much like filler materials. Fibres also tend to bulk the bitumen
so it will not run off from the aggregates during construction.
Previous researches (Marais, 1979; Chen and Lin, 2005; Amit and Animesh 2004;
Tapkin, 2008) showed that the addition of fibre into bitumen increases the stiffness of the
bitumen binder resulting in stiffer mixtures with decreased binder drain down. The fibre
modified mixtures showed improved Marshall properties with increased stability and bulk
specific gravity values compared to the control mix.
Fibres appear to have the potential to improve fatigue life and deformation characteristics
by increasing rutting resistance. The tensile strength and related properties of mixtures
containing fibres were found to improve. In terms of workability, mixtures with fibres showed a
slight increase in the optimum binder content compared to the control mix. This is similar to the
addition of very fine aggregates. The proper quantity of bitumen needed to coat the fibres is
dependent on the absorption and the surface area of the fibres and is therefore affected not only
by different concentrations of fibres but also by different fibre types (Button and Lytton, 1987).
According to Mills and Keller (1982), the degree of homogeneity of dispersion of the
fibres within the mix will determine the strength of the resulting mixtures. The results obtained
from the different field studies showed that the addition of fibre have a benefit since it will help
to produce more flexible mixtures with more resistant to cracking (Jiang et al., 1993).
The design methods of bituminous mixtures primarily include the well-known Marshall
design method and Superpave design method. In the design procedure bitumen content plays a
key role in determining the engineering properties of mixture, which is determined in terms of
the volumetric properties of mixture (specific gravity, air void, etc.) in both the Marshall and
Superpave mixture design procedures. However, the volumetric properties of fibre-reinforced
bitumen mixture are different from that of the ordinary bituminous mixture (Serfass and
Samanos, 1996).

13
Therefore, it is essential to investigate the volumetric properties of these mixtures to design more
reliable ones. Fibre content plays an important role in determining the volumetric and
engineering properties of bituminous mixtures. It was reported that there exists some optimum
fibre content to achieve the maximum tensile strength and toughness (Chen et al., 2004). In
many cases, fibre content is determined only according to the engineering practices or
manufacturer’s recommendation.
Bushing and Antrim (1968) used cotton fibres in bituminous mixtures. These were
degradable and were not suitable as long term reinforcement. Metal wires has been proposed by
Tons and Krokosky (1960), but they were susceptible to rusting with the penetration of water.
Asbestos fibres were also used in pavement mixes until it was determined as a health hazard
(Kietzman, 1960; Marais, 1979). With the new developments in the technology of production,
natural fibre reinforced bituminous mixtures can be cost competitive when compared with
modified binders.
The natural coir fibre which is a cheaper and an ecofriendly alternative to synthetic fibre,
can be effectively used as a stabilizing additive in bituminous concrete (Bindu and Beena, 2009).
The percentage increase in retained stability of the mixture as compared to the conventional mix
was about 14% at the optimum fibre content of 0.3% and the reduction in bitumen content is 5%
giving an appreciable saving in binder.
Bituminous pavements have experienced accelerated deterioration due to traffic growth
and climatic conditions. When a load is applied to the surface of a bituminous pavement it
deforms. But bitumen, being a viscoelastic material, the majority of the deformation recovers
when the load is removed. However, there is a minute amount of irrecoverable viscous
deformation which remains in the bitumen and which results in a very small permanent residual
strain.
Accumulation of millions of these small strains due to axle loading results in the surface
rutting familiar on heavily trafficked pavements. Laboratory tests that attempt to measure the
rutting resistance, i.e., the resistance to permanent deformation of a bituminous mix, are: the
Marshall test, static and dynamic creep tests, wheel-tracking tests, and laboratory test track tests
(Robertus et al., 1995). Bitumen with polymers form multiphase systems, which usually contain
a phase rich in polymer and a phase rich in bitumen not absorbed by the polymer.
The properties of bitumen-polymer blends depend on the concentrations and the type of
polymer used. The polymer is usually loaded in concentrations of about 4–6% by weight with
respect to the bitumen. Higher concentrations of polymers are considered to be economically less
viable and also may cause other problems related to the material properties.

14
LITERATURE REVIEW
Annually, a steady stream of large volume of waste tires is generated due to the continual
increase in the number of all kinds of transport vehicles. Especially for the European Community
(Austria, Belgium, Denmark, Finland, France, Germany, Greece, Holland, Ireland, Italy,
Luxembourg, Portugal, Spain, Sweden, UK), this amount is estimated at up to 250 million waste
tires, while equal amounts are estimated for East Europe, North and Latin America, Japan and
Middle-East. In addition to this, 3 billion of EOL Tires have already been stockpiled or land
filled inside the EC and almost 1 billion in North America. In Greece, the annual deposit of
worn mobile tires comes up to 58,500 - 70,000 , causing a major environmental problem.
Because of the increase in the number of tires accumulating around the world and
environmental hazards associated with them, more nations are looking for ways to make use
of this waste product. Tire rubber can be used in various civil engineering applications, such as
for the production of pastes, mortars and concrete based on cement, based on bituminous binder
or soil. Studies so far, show that utilization of recycled rubber from worn mobile tires in the road
construction sector can be a very promising and environmentally friendly way to eliminate the
nations’ stock of scrap tires.
Rubberized asphalt is a process of incorporating fine crumb rubber particles with
asphalt paving materials. The processes of applying crumb rubber from tire waste in bituminous
mixtures can be divided into two categories: the dry process and the wet process. In the dry
process, crumb rubber is added to the aggregates before introducing the asphalt binder to the
mixture, i.e. crumb rubber acts as a partial replacement to some of the aggregate sizes. In the
wet process, bituminous binder is pre-blended with tire rubber at high temperature (150˚C -
210˚C) and under specific blending conditions. Crumb rubber particles in the dry process are
normally coarser than those in the wet one because they are considered as part of the aggregate
gradations.
Whereas, in wet process, fine crumb rubber powders fully react with bituminous binders
and improve the binder properties. In Greece, the use of rubber in asphalt pavements is still a
nationally relatively unexplored area with many according to world wide literature advantages.
This is remains under-utilized mostly due to lack of knowledge of the technical world.
Rubberized asphalt provides a safer, smoother and quieter road surface. The main theme
of this paper is the effectiveness of rubberized asphalt as traffic noise mitigation measure. In the
frame of life project with Acronym roadtire (Integration of end-of-life tires in the life cycle of
road construction), co-funded by the European Commission, a pilot project of the design and
construction of rubberized asphalt pavement has been conducted, after extensive laboratory
research. A road section in the city of Lamia in the region of Sterea El- lada-Vasilikon street,
was selected for the pilot application.

15
The upper bituminous layer of the pavement has been made of rubberized bituminous
mixture produced by the wet process and its basic properties are presented. However, present
paper focuses on data concerning traffic noise level during various time periods of a day and
theirs’ comparison on conventional pavements and rubberized one of Vasilikon street, which is
characterized by heavy traffic.
Rubberized bituminous top layers having pavements are called "flexible" since the total
pavement structure "bends" or "deflects" due to traffic loads. This pavement structure generally
composed of several layers of materials which can accommodate this "flexing". In this type of
pavements, material layers are usually arranged in the order of descending load bearing capacity
with the highest load bearing capacity material (and most expensive) on the top and the lowest
load bearing capacity material (and least expensive) on the bottom. The surface course is the
stiffest and contributes the most to the pavement strength. The underlying layers are less stiff but
are still important to pavement strength as well as drainage and frost protection. A typical
flexible pavement structure consists of surface course, base course and sub base course
(optional).
The surface course is the top layer in contact with traffic loads. This layer provides the
characteristics such as friction, smoothness, noise control, rut resistance and drainage. In
addition, it serves to prevent the entrance of excess quantities of surface water into the
underlying base, sub base and sub grade courses (NAPA, 2001). The topmost layer of the surface
course which is in direct contact with traffic loads is the wearing course. This can be removed
and replaced as and when it becomes damaged or worn out.
The wearing course can be rehabilitated before distress propagates into the underlying
intermediate / binder course. This layer which constitutes the major portion of the surface course
is meant to distribute the load coming over it. The base course is the layer directly below the
surface course which helps in transmitting the load to the sub grade and generally consists of
aggregate either stabilized or unstabilized.
Bituminous mixes like Hot Mix Asphalt can also serve as a base course. Under the base
course layer, a layer of less expensive / inferior quality material can be provided as sub base
course material over the sub grade. The sub base course is optional in many cases. Bituminous
mixtures can be classified by their method of composition and characteristics as Dense-Graded
HMA, Open-Graded HMA and Stone Matrix Asphalt. Dense-graded mixtures has a dense-
graded aggregate gradation (aggregates are evenly distributed from coarse to fine) and have a
relatively low air voids after placement and compaction. They are commonly used as surface and
binder courses in bituminous pavements. Bituminous concrete is commonly used to refer to a
high-quality, dense-graded HMA mixture. A dense graded HMA mixture with maximum
aggregate size of greater than 25 mm is called a large stone dense-grade HMA mix, whereas a
mix with 100% of the aggregate particles passing through the 9.5mm sieve is called a sand mix.

16
Unlike dense-graded mixes, an open-graded HMA mixture has a relatively larger size
aggregate that contains very little or no fines, they are designed to be water permeable. Due to
less aggregate surface area, these mixes have relatively lower bitumen content than that of a
dense-graded HMA mix.
Stone Matrix Asphalt (SMA) is a gap graded bituminous mixture containing a high
proportion of coarse aggregates and filler with relatively less medium sized aggregates. It has
high binder content and low air voids with high levels of macro texture when laid resulting in
waterproofing with good surface drainage.
For a comparison, a view of a typical SMA mixture and a conventional dense graded
mixture cores from SMA mixtures (left) illustrate the greater percentage of fractured aggregate
and higher percentage of bitumen binder, compared to the conventional Hot Mix Asphalt (HMA)
mixture (right) which contains a more uniform aggregate gradation and less bitumen binder.
Bitumen modification / reinforcement have received considerable attention as viable
solutions to enhance flexible pavement performance. The introduction of this technology to the
transportation industry was mainly prompted by the unsatisfactory performance of traditional
road materials exposed to remarkable increase and changes in traffic patterns. Since then,
various types of modifiers for bituminous mixtures like fibres and polymers are considered. It
has been possible to improve the performance of bituminous mixes used in the surfacing course
of road pavements, with the help of various types of stabilizing additives. The additives such as
fibres, rubbers, polymers, carbon black, artificial silica, or a combination of these materials are
used to stiffen the mastic at high temperatures during production and placement, and to obtain
even higher binder contents for increased durability.
Since Stone Matrix Asphalt is the focus of the present study, the literature pertaining to
that has been presented as a separate session after this. The following is a review of the work
done in bituminous mixes stabilized with various additives. Some fibres have high tensile
strength relative to bituminous mixtures, thus it was found that fibres have the potential to
improve the cohesive and tensile strength of mixes. They are believed to impart physical changes
to bituminous mixtures (Brown et al., 1990). Research and experience have shown that fibres
tend to perform better than polymers in reducing the drain down of bituminous concrete
mixtures that is why fibres are mostly recommended (Hassan et al., 2005). Because of the
inherent compatibility of fibres with bitumen and its excellent mechanical properties, adding
fibres to bitumen enhances material strength and fatigue characteristics while at the same time
increasing ductility.

17
According to Maurer and Gerald, fibre reinforcement is used as a crack barrier rather than
as a reinforcing element whose function is to carry the tensile loads as well as to prevent the
formation and propagation of cracks. Finely divided fibres also provide a high surface area per
unit weight and behave much like filler materials. Fibres also tend to bulk the bitumen, so it will
not run off from the aggregates during construction. In terms of efficiency, mixtures with fibre
showed a slight increase in the optimum binder content compared to the control mix. In this way,
adding fibres to bitumen is very similar to the addition of very fine aggregates to it. Thus, fibre
can stabilize bitumen to prevent leakage.
The authors concluded that the decreased susceptibility to moisture related distress in the
porous mixtures tested is due to better drainage. In the second study, two million load
applications were applied to fibre-modified bituminous mixture which was used as an overlay on
pavements with signs of fatigue distress. After the load applications, the pavement surface was
noted to have a well maintained macrostructure, and practically no cracking. Fibre modified
overlays were also constructed over fatigued pavements in the third study reported by them.
After 1.2 million load applications, it was observed that all of the fibre modified overlays
showed no sign of fatigue related distresses or rutting compared to the unmodified samples
which showed signs of distress. This was in agreement with the findings of the second study,
establishing that the fatigue life of the fibre modified pavement is improved over unmodified
mixtures. Fibre modification also allowed for an increase in film thickness, resulting in less
ageing and improved binder characteristics. Addition of fibres also resulted in the reduction of
temperature susceptibility of bituminous mixtures.
The design methods of bituminous mixtures primarily include the well-known
Marshall design method and Superpave design method. In the design procedure bitumen content
plays a key role in determining the engineering properties of mixture, which is determined in
terms of the volumetric properties of mixture (specific gravity, air void, etc.) in both the Marshall
and Superpave mixture design procedures. However, the volumetric properties of fibre-
reinforced bitumen mixture are different from that of the ordinary bituminous mixture (Serfass
and Samanos, 1996). Therefore, it is essential to investigate the volumetric properties of these
mixtures to design more reliable ones. Fibre content plays an important role in determining the
volumetric and engineering properties of bituminous mixtures. It was reported that there exists
some optimum fibre content to achieve the maximum tensile strength and toughness.
Bituminous pavements have experienced accelerated deterioration due to traffic growth
and climatic conditions. When a load is applied to the surface of a bituminous pavement it
deforms. But bitumen, being a viscoelastic material, the majority of the deformation recovers
when the load is removed. However, there is a minute amount of irrecoverable viscous
deformation which remains in the bitumen and which results in a very small permanent residual
strain. Accumulation of millions of these small strains due to axle loading results in the surface

18
rutting familiar on heavily trafficked pavements. Laboratory tests that attempt to measure the
rutting resistance, i.e., the resistance to permanent deformation of a bituminous mix, are: the
Marshall test, static and dynamic creep tests, wheel-tracking tests, and laboratory test track tests.
Bitumen with polymers form multiphase systems, which usually contain a phase rich in polymer
and a phase rich in bitumen not absorbed by the polymer. The properties of bitumen-polymer
blends depend on the concentrations and the type of polymer used. The polymer is usually
loaded in concentrations of about 4–6% by weight with respect to the bitumen. Higher
concentrations of polymers are considered to be economically less viable and also may cause
other problems related to the material properties (Giovanni et al., 2004).
Polymers are long-chain molecules of very high molecular weight, used by the binder
industry. These can be grouped into three main categories: thermoplastic elastomers, plastomers,
and reactive polymers based on the mechanism of resistance to deformation. Thermoplastic
elastomers are obviously able to confer good elastic properties on the modified binder, while
plastomers and reactive polymers are added to improve rigidity and reduce deformations under
the load.
For a polymer to be effective in road applications, it should blend with the bitumen and
improve its resistance to rutting, abrasion, cracking, fatigue, stripping, bleeding, ageing, etc. at
medium and high temperatures without making the modified bitumen too viscous at mixing
temperatures or too brittle at low temperatures. It can also blend with aggregate and heated so as
to have a coating on the aggregate which leads to an improvement in the overall performance of
the pavement. Many polymers have been used in the modification process but thermoplastic
elastomers are enjoying wide acceptance as road bitumen modifiers.
The load-deformation behavior of elastomers is similar to that of a rubber band which
regains its initial state after the removal of load. Plastomers, on the other hand, exhibit high early
strength but are less flexible and are more prone to fracture under high strains than elastomers.
Examples of the plastomeric types of polymers for bitumen modification are polyethylene (PE),
ethylene-vinyl acetate (EVA), and ethylene-butyl acrylate (EBA) random copolymers. Polymers
have been utilized for the purpose of improving the high and low temperature characteristics of
bituminous compositions, as well as to improve their toughness and durability.
Additives such as styrene based polymers, polyethylene based polymers, polychloroprene,
gilsonite, various oils, and many other modifiers including tall oil have been added to bitumen to
enhance various engineering properties of binder. Marshall stability tests were conducted on
samples after soaking in water at 60˚C for 24 hours to study the water induced damages.
Considerable resistance to water induced damages was observed for the samples.

19
METHODOLOGY
In the frame of life project with Acronym road tire (Integration of end-of-life tires in the life
cycle of road construction), co-funded by the European Commission, a pilot project of the
design and construction of rubberized asphalt pavement has been conducted, after extensive
laboratory research. A road section in the city of Lamia in the region of Stereo Elide Vasilikon
street, was selected for the pilot application. The upper bituminous layer of the pavement has
been made of rubberized bituminous mixture produced by the wet process and its basic
properties are presented. However, present paper focuses on data concerning traffic noise level
during various time periods of a day and theirs’ comparison on conventional pavements and
rubberized one of Vasilikon street, which is characterized by heavy traffic.
Materials:
Rubberized asphalt is composed of asphalt/bituminous binder, in which tire rubber is
added at various percentages, in order to obtain a uniform final product, which is called the
rubberized asphalt. This new product requires higher mixing temperatures compared to the
conventional one, as well as increased mixing time. Preliminary mix design should aim at
rubberized binders with:
1) Relatively low viscosity, so as to compact easily.
2) Elasticity as common elastomeric binder.
3) Penetration and R&B (Ring & Ball) test similar to the common elastomeric binder.
4) To be as homogeneous as possible (which means very fine rubber particles included).
Moreover, rubber particles should have high specific surface, while time and temperature
of mixing during production should be technically reasonable (acceptable from binder’s
production units).
In the frame of this research, various series of rubberized asphalt—with and without
additives have been produced and examined in the lab. All procedures have taken place at the
Department of Materials Testing and Control of Quality of Public Works of Stereo Elide in
cooperation with Laboratory of Building Materials, of the Department of Civil Engineering of
Aristotle University of Thessaloniki.
Mixing temperature for all binders (conventional and rubberized ones) ranged from
150˚C - 210˚C depending on the percentage of tire rubber included, while mixing time was kept
constant at 2 hours. Properties examined included: penetration, softening point (ring and ball
test), viscosity, elastic recovery, ductility and stereoscopic examination, while all tests have been
conducted according to existing test/control standards. Taking into ac- count all the rheological
characteristics examined, the composition which behaved best to all properties and which has

20
been further suggested for the pilot application was the special modified rubberized binder with
the addition of tire rubber at 10%wt. This binder is produced under special designed and
controlled production conditions. In particular, the special process ensures maximum possible
swelling and dispersion of tire rubber into the bitumen, in order to have a final binder with high
elastomeric properties and high softening point.
Bitumen is mixed with tire rubber powder, into special designed high shear mixers at
(1000 rpm) for 2 hours, at a temperature of ≤180˚C - 185˚C in order to avoid fumes. Successful
mixing in such temperature values can be accomplished with the addition of a small percentage
of special additive/s suggested percentage 3%w/t that are reducing the mix viscosity. After
mixing time, the product is passing through a colloid mill of ~3000 rpm in order to ensure
further dispersion of the tire rubber powder. High shear mixers are vertical cylindrical vessels
of 15 cubic meters capacity, having a high speed revolving screw type axis, able to spin with
1000 rpm at full capacity, with a liquid of more than 10.000 cPs viscosity. Parallel to mixing, the
blend can be recalculated internally, through a homogenizer colloid mill in order to obtain the
maximum dispersion of the crumb rubber on the one hand, while on the other, possible bigger
particles of rubber can be reduced in size, promoting this way the better reaction of rubber with
bitumen.
With these mixing facilities, one can obtain both maximum interaction of rubber with
bitumen, and take advantage of its elastic properties. Conventional mixing will only entrap the
crumb rubber into the bituminous binder and the crumb rubber will act only as filler into the
asphalt mix. The colloid mill is of the same design as the ones used for the bituminous
emulsions production. It consists of a disk stator, equipped with metal teeth, and a high speed
rotor (3000 rpm) with the same teeth type, having a gap of only 10 microns as they pass through
the teeth of the stator. The blend is forced to recirculate through these teeth, ensuring fast and
maximum reaction, as well as, minimum size of crumb rubber in presence. After approximately
2 hours, viscosity of the blend rises, since reaction finishes. High viscosities can create
compaction problems afterwards, and the only way to overcome this, is by increasing
compaction temperature, or by incorporating viscosity reducers of the paraffin wax type of
hydro- carbons (C-10 to C-12).
For the purpose of this research, viscosity reducer additives have been used since they
are more environmentally friendly, keeping this way compaction temperature at normal levels,
minimizing fume exposure. Characteristics of specific binder used for the pilot application as
well as of conventional one are shown on table-1.
It must be noted that the city of Lamia in central Greece, where pilot application took
place by implementing rubberized bituminous mixture, has high summer-time temperatures,
considerably low winter-time temperatures, and medium to heavy traffic loads, so elasticity,
elevated Softening Point and high stiffness of the modified binder, were properties highly
required for the design of the mixture to be used. That way, mainly Mediterranean countries,

21
with similar temperature and operative conditions, can use ROADTIRE’s technology. The
mixture used for the pilot application has been produced by the wet process, which means that
modified rubberized bitumen has been used as the bituminous binder.
Table 1. Characteristics of binder used for the pilot application as well as of conventional one
During this process, tire rubber particles modify the rheological characteristics of the
binder, as mentioned above. This modification is attributed to physical and compositional
changes due to the interaction between rubber particles and the bituminous binder. In many
countries such as America and in some European ones (e.g. Italy, Spain, Germany etc.), the wet
process is a very common method used to produce rubberized asphalt concrete with improved
characteristics such as noise reduction and longer pavement life with reduced maintenance costs.
Specifically, bituminous mixture used, for the pilot application in the city of Lamia, was
a dense graded one containing 5% modified bituminous binder. The produced mixture consisted
of rubberized bitumen and natural aggregates. As far as the bituminous binder is concerned, it
was a special one, capable of accepting modification by tire rubber particles. This binder is
produced by the addition of 10% w/t of Tire Rubber Powder (0 - 1 mm), under special designed
and controlled production conditions in conventional bituminous binder 50/70. Aggregates used
were of limestone origin from a quarry near the city of Lamia. As far as the bituminous mixture
is concerned, it was produced and tested at the Laboratory of the Department of Material’s
Control and Public Works’ Quality of Sterea Ellada in cooperation with Laboratory of Building
Materials of the Department of Civil Engineering of Aristotle University of Thessaloniki
according to European and Greek specifications, which are in force for conventional bituminous
mixtures and for surface bituminous layer.
Tests on properties of raw materials (aggregates and tire rubber) took also place at the
above laboratories, while all values of properties examined complied with relevant
specifications. Furthermore, rutting resistance has been examined according to ΠΕΤΕΠ based
on Bituminous Mixtures-Tests methods for hot mix asphalt wheel tracking. The Federal
Highway Administration and many state agencies have conducted numerous field studies for the
feasibility of using recycled tire rubber products in HMA pavements. Several test cases in the
US (California, Texas, Florida) have shown reductions in pavement noise when compared to
conventional, without rubber, asphalt pavements. The European Standard followed for this test
Rheological characteristic Value for rubberized bitumen (pilot application) Value for conventional 50/70
Penetrationat 25˚C, pen 39 55
Softeningpoint, ˚C 67 46
Ductility at 25˚C, cm 31 110
Viscosity at ~1000cps, ˚C 180 123
Elastic recovery,% ≥60 10

22
describes test method for determining the susceptibility of bituminous materials to deform under
load. Studies conducted internationally have shown that rubberized asphalt can reduce;
associated with roadway traffic, noise pollution. This phenomenon was first noted in Belgium,
in 1981, where studies on asphalt rubber hot mix showed a dramatic reduction in noise levels.
As a result, countries around the world have started noise level studies in order to evaluate the
validity of claims being made. In many cases, a reduction in highway noise was evident even
after widening of the roadway, resulting in higher traffic volumes and speeds. In Arizona, the
excellent noise-reducing properties have been highlighted and have been a major driver for
replacing much of constructed concrete surfaces by rubberized asphalt bituminous ones. A type
of dense asphalt with a high content of polymer-modified binder (the amount of rubber in the
surface is around 1.5% by weight) has been developed and used with excellent acoustic
properties.
Figure 1. Pilot project of Vasilikon Street
Procedure and equipment Measurements
Street’s preparation actions included the removal of old surface bituminous layer by the
use of appropriate machinery and cleaning by the use of brush. Before laying of the new asphalt
layer, tack coating took place, so as to enhance bonding between the remained old asphalt layer
of the road pavement and the new one. Finally the pilot application was completed by
compaction of the new layer with the rubberized bituminous mixture. All preparatory actions as
well as actions during the implementation have been supervised by engineers from municipality
of Lamia and engineers from Laboratory of Building Materials.
The main scope of this research was to find out if the implementation of a layer of
rubberized asphalt could reduce the noise pollution that is associated with the road traffic and
whether or not this reduction remains in time. Two measurement points for Vasilikon street were
selected based on their accessibility as well as on characteristics related to typical conditions
primarily in the ambient noise level and road geometry. The measurement locations were

23
selected to be as generically representative as possible, characterized by a free flow of vehicles,
with constant speed, without traffic lightings nearby. The mean vehicle speed was 40 km/h,
while the environmental temperature ranged between 7˚C and 12˚C during the measurements.
One point of the road was in the conventional asphalt pavement and the other in the rubberized
one. Noise measurements were conducted, by positioning the microphone at a height of 0.30 m,
away from intersections so as to ensure accurate measurements and to enhance the pavement
noise source (traffic noise is generated primarily by the interaction of the tires and the pavement
(78%), engine and exhaust noise (12%), and aerodynamic effects (10%)).
Two Noise Level Analyzers type 2237 “Brüel & Kjær” were used, according to
recommendations of International Standard Organization for the measurement of traffic noise,
for each point measurement, together with a calibrator used to guarantee measurement accuracy.
The noise level meters were programmed to continuously measure the A-weighted noise level
and store the energy-equivalent noise level (Leq). The acoustic survey was carried out in two
consecutive working days for three different time intervals. Specifically, the first survey-time
intervals were between 10:00 a.m. and 12.00, the second survey-time interval from 12:00 to
02:00 p.m. and the third survey-time interval from 06:00 p.m. to 08:00 a.m. Time interval of
each measurement was 10 min, time long enough for the statistical levels to remain stable in
this type of measurement and situation. The level of noise (Leq) was measured three
consecutive times, for each point, of the same 10-minute period. The final value (Leq) is the
average of the three 10-minute period.
Figure.2- Removal of the old surface and cleaning at Vasilikon Street
Unlike dense-graded mixes, an open-graded HMA mixture (Figure.2) has a relatively
larger size aggregate that contains very little or no fines, they are designed to be water
permeable. Due to less aggregate surface area, these mixes have relatively lower bitumen content
than that of a dense-graded HMA mix.

24
CLASSIFICATION OF BITUMINOUS MIXTURES
A bituminous mixture is a combination of bituminous materials (as binders), properly
graded aggregates and additives. Bituminous mixtures used in pavement applications are
classified either by their methods of production or by their composition and characteristics.
By the method of production, bituminous mixtures can be classified into Hot-mix asphalt
(HMA), Cold-laid plant mix, Mixed-in-place or road mix and Penetration macadam. Hot-mix
asphalt is produced in hot asphalt mixing plant (or hot-mix plant) by mixing a properly
controlled amount of aggregate with a controlled amount of bitumen at an elevated temperature.
Figure.3- Basic flexible pavement structure
The mixing temperature has to be sufficiently high such that the consistency of bitumen
is fluid enough for proper mixing and coating the aggregate, but not too high as to avoid
excessive stiffening of the asphalt. HMA mixture must be laid and compacted when the mixture
is still sufficiently hot so as to have proper workability. They are the most commonly used
paving material in surface and binder courses in bituminous pavements. Cold-laid plant mix is
produced in a bitumen mixing plant by mixing a controlled amount of aggregate with a
controlled amount of liquid bitumen without the application of heat. It is laid and compacted at
ambient temperature. Mixed-in-place or road mix is produced by mixing the aggregates with the
bitumen binders in the form of emulsion (medium setting or slow setting) in proper proportions
on the road surface by means of special road mixing equipment.
Penetration macadam is produced by a construction procedure in which layers of coarse
and uniform size aggregate are spread on the road and rolled, and sprayed with appropriate
amounts of bitumen to penetrate the aggregate. The bituminous material used may be hot
bitumen or a rapid setting bitumen emulsion. Bituminous mixtures can be classified by their

25
method of composition and characteristics as Dense-Graded HMA, Open-Graded HMA and
Stone Matrix Asphalt (SMA). Dense-graded mixtures (Figure.4) has a dense-graded aggregate
gradation (aggregates are evenly distributed from coarse to fine) and have a relatively low air
voids after placement and compaction. They are commonly used as surface and binder courses in
bituminous pavements. The term bituminous concrete is commonly used to refer to a high-
quality, dense-graded HMA mixture. A dense graded HMA mixture with maximum aggregate
size of greater than 25 mm is called a large stone dense-grade HMA mix, whereas a mix with
100% of the aggregate particles passing through the 9.5mm sieve is called a sand mix.
Figure.4- Dense graded HMA, Figure.5- Open graded HMA, Figure.6- Stone Matrix Asphalt
Danse graded mixes, an open-graded HMA mixture (Figure.5) has a relatively larger size
aggregate that contains very little or no fines, they are designed to be water permeable. Due to
less aggregate surface area, these mixes have relatively lower bitumen content than that of a
dense-graded HMA mix.
Stone Matrix Asphalt (SMA) is a gap graded bituminous mixture containing a high
proportion of coarse aggregates and filler with relatively less medium sized aggregates
(Figure.6). It has high binder content and low air voids with high levels of macro texture when
laid resulting in waterproofing with good surface drainage.
For a comparison, a view of a typical SMA mixture and a conventional dense graded
mixture (NAPA, 1999) is shown in Figure.7. Cores from SMA mixtures (left) illustrate the
greater percentage of fractured aggregate and higher percentage of bitumen binder, compared to
the conventional Hot Mix Asphalt (HMA) mixture (right) which contains a more uniform
aggregate gradation and less bitumen binder of bituminous mixes used in the surfacing course of
road pavements, with the help of various types of stabilizing additives. The additives such as
fibres, rubbers, polymers, carbon black, artificial silica, or a combination of these materials are
used to stiffen the mastic at high temperatures during production and placement, and to obtain
even higher binder contents for increased durability (Pierce, 2000).

26
Figure.7- Comparisons between SMA and conventional HMA
Since Stone Matrix Asphalt is the focus of the present study, the literature pertaining to
that has been presented as a separate session after this. The introduction of this technology to the
transportation industry was mainly prompted by the unsatisfactory performance of traditional
road materials exposed to remarkable increase and changes in traffic patterns. Since then, various
types of modifiers for bituminous mixtures like fibres and polymers are considered. The natural
coir fibre which is a cheaper and an ecofriendly alternative to synthetic fibre, can be effectively used
as a stabilizing additive in bituminous concrete (Bindu and Beena, 2009). The percentage increase in
retained stability of the mixture as compared to the conventional mix was about 14% at the optimum
fibre content of 0.3% and the reduction in bitumen content is 5% giving an appreciable saving in
binder.
The growth in various types of industries together with population growth has resulted in
enormous increase in the production of various types of waste materials, world over. The
creation and disposal of non-decaying waste materials such as blast furnace slag, fly-ash, steel
slag, scrap tyres, plastics etc., have been posing difficult problems in developed as well as in
developing countries. Considerable work has been done in various countries for the disposal and
utilization of some of these waste products (Schroceder, L.R., 1994). Among them, the work
done in India, particularly at the Central Road Research Institute (CRRI), New Delhi on the use
of waste materials like fly-ash and slag in road construction is note worthy.
Marshall stability tests were conducted on samples after soaking in water at 60˚C for 24
hours to study the water induced damages. Considerable resistance to water induced damages
was observed for the samples. The average stability value of the BC mix with modified binder
was found to increase by about 2.6 times of the mix with ordinary bitumen. Further laboratory
studies on the BC mixes using this modified binder also indicated considerable increase in
fatigue life under repeated application of loads.

27
DESIGN AND ANALYSIS
Traffic monitoring was conducted by making manual vehicle counts. The traffic counts were
made continuously during the 10-minute noise measurement periods at each point survey. The
vehicle classification included passenger cars, heavy trucks and motorcycles. When the traffic
monitoring and the corresponding level of noise of each point were conducted, the other lane of
street was out of traffic. For this purpose, the help of municipal au- thorities and police was
significant and necessary in order to obtain reliable measurements. Traffic and vehicles’
distribution, where it can be noticed that Vasilikon Street is characterized by the high number of
trucks and the higher speed rate, especially in the “rubberized asphalt road section”. Number of
cars counted in the three point surveys varied; especially, number of trucks and motorcycles
differed significantly.
In order the measured noise levels to be correlated to an equivalent number of vehicles at
each site, an Equivalent Number of Vehicles (EN) was used, so that the actual change in traffic
noise level could be obtained. This Equivalent Number of Vehicles was elaborated by the
Highway Laboratory of Civil Engineering of Aristotle University of Thessaloniki.
Noise Leq with the level of noise that the different categories of traffic produce. The
different coefficients of the parameters were based on the European Union legislation on
environmental noise and the upper limits of noise exposure of different means of transport
(namely the upper limit of noise exposure of car is 74 dB, the upper limit of truck is 80 dB and
the upper limit of motorcycle is 77 dB). Moreover, for an urban area, heavy vehicles have been
assumed to generate a noise that is ten times louder than cars’ one according to the European
Commission. This value of EN is computed from:
EN = Nv + 3⋅ NL +10 ⋅NH , where-
EN = Equivalent Number of Vehicles;
NV = Number of Passenger Vehicles ;
NL =The Total Number of Motorcycles;
NH =It Indicates total Number of Trucks
The results of noise and traffic measurements in Vasilikon Street, for the two
measurement points are summarized in measurements of (Leq) for immediately after the laying
of the modified top surface layer as well as 8 months after its operation. The average measured
sound levels obtained in each survey are compared to the corresponding equivalent number of
vehicles of each time-period survey. The combination of the equivalent number of vehicles and
the corresponding traffic level of noise, during the two period of survey, after construction of the
pavement and 8 months later.

28
Analysis of the results shows that, generally, the rubberized asphalt pavement performs
better than the conventional one as far as reduction on traffic noise level is concerned. The
values of noise range from 73 - 71 dB in conventional asphalt pavement and 70 - 68 dB in
rubberized asphalt pavement. The measured difference is about 1 - 3 dB. It is remarkable that,
despite the dense gradation of the pavement surface, it is obvious a reduction in noise level.
Moreover, this improved performance of the rubberized asphalt pavement compared to
the conventional one remained the same even 8 months after its operation. The results of noise
reduction could be enhanced if open-graded rubberized bituminous mixture was implemented.
However, the good noise performance of rubberized asphalt pavement has been minimized a bit,
after a period of 8 months.
Moreover, in order the measured noise levels to be correlated to an equivalent number of
vehicles at each site, an Equivalent Number of Vehicles (EN) was used, in order to obtain the
actual change in traffic noise level.
Results of noise surveys conducted on the rubberized and conventional pavements, when
compared, indicate that the use of rubberized bituminous mixtures can reduce traffic noise
exposure levels by 1 to 3 dB. This reduction can be attributed to rubber particles structure and
characteristics, as well as in the special mixing conditions for the preparation of the modified
binder, which has been followed in present paper and is unique not only for Greece but for most
of the European countries as well.
Moreover, when one considers that the decibel scale is logarithmic of every increase of
ten decibels means a sound twice as loud as the former one of these numbers represent
significant decreases on traffic noise at the pavement itself. Advantage of the use of such
bituminous mixture has been also certified by citizens and especially drivers, who mentioned
the better performance of the lane, with the modified rubberised asphalt mixture as far as noise
level and comfort in travelling is concerned.
The results of noise reduction could be enhanced if open-graded rubberized bituminous
mixture was implemented, which means by the use of other types of aggregates’ gradations,
natural and recycled ones (derived from Construction and Demolition Wastes-C&D W-),
leading to combined utilization of two waste streams (EOL Tires and C&D W).
SMA is a blend of crushed coarse aggregate, crushed fine aggregate (or sand), mineral
filler, bitumen binder and stabilizing agent. These major components of SMA mixtures are
shown in Fig. 2.6. A stone skeleton mixture that, when compacted, provides the gap-graded
stone-on-stone structure to carry heavy traffic loads, prevent rutting, and provides long term
durability.

29
` The mineral filler, fine aggregate and bitumen provides the binder adhesive to bond the
stone skeleton together and to provide a cohesive mixture. Finally, additives such as fibres or
polymers are used as a stabilizer to secure the mastic within the overall structure.
They stiffen the resulting mastic and prevent the draining off during storage,
transportation and placing of SMA. The mastic fills the voids, retains the chips in position and
has an additional stabilizing effect as well as providing low air voids and thus resulting in highly
durable bitumen.
Mineral fillers and additives play the role of minimizing the binder drain down,
increasing the amount of binder used in the mix and improving the mix durability.
The SMA mixtures are composed to have a high coarse aggregate content (typically 70-
80%), a high bitumen content (typically over 6%) and high percentage of mineral filler content
(approximately 10% by weight). High coarse aggregate content results in stone-on-stone contact
that produces a mixture that is highly resistant to rutting.
These gap graded bituminous mixtures (minimizing medium sized aggregates and fines)
result in a structurally tough skeleton In summary, the high stone content forms a skeleton type
mineral structure which offers high resistance to deformation due to stone to stone contact,
which is independent of temperature.
Figure. 9- Major components of SMA mixture
Selection of materials is important in SMA design. The coarse aggregate should be a
durable, fully crushed rock with a cubicle shape (maximum of 20% elongated or flat aggregate).
Fine aggregate should be at least 50% crushed.

30
Filler can be ground limestone rock, hydrated lime or flyash. In general, materials of
similar quality to those used in dense graded bituminous wearing courses are required.
Figure.10- SMA aggregate skeleton (NAPA, 1999)
Mineral filler is that portion passing the 0.075 mm sieve. It will usually consist of finely
divided mineral matter such as rock dust, Portland cement, hydrated lime, ground limestone dust
or fly ash. Mineral filler is essentially stiffening the rich binder SMA. A higher Percentage of
filler may stiffen the mixture excessively, making it difficult to compact and may be resulting in
a crack susceptible mixture, (Brown and Haddock, 1997).
In general, amount of material passing through the 0.075 mm sieve is relatively 8-12
percent of the total amount of aggregate in the mix. Since the amount of material passing through
the 0.075-mm sieve is relatively large, the SMA mixtures perform very differently from other
HMA mixtures. These fines, along with the bitumen and fibre, make the mastic which holds the
mix together. SMA mixtures are very sensitive to the amount of 0.075 mm (No. 200) in the mix.
Handling, storing and the introduction of the mineral filler is therefore an important concern.
The type of fines can also affect drain down. Brown and Mallick (1994) found that
baghouse fines had much less drain down than mixtures containing marble dust. This is because
the smaller particles provide more surface area for a given weight and thus tend to stiffen the
binder more than coarse fines. This clearly shows the importance of the size of the particles
passing the 0.075 mm sieve in SMA. Stone matrix asphalt contains more binder than
conventional dense graded mixes, with percentages ranging from about 6.0% to 7.5%. The
performance of the mix is usually enhanced with polymers and fibres.

31
These help to provide a thick coating to the aggregate and to prevent the drain down
during transportation and placement. Polymer modified binders can be used to give even greater
deformation resistance. Brown et al. (1997a) reported that SMA incorporating styrene butadiene
styrene produced more rut resistant mixes than SMA with unmodified binder. Superior fatigue
lives are also reported.
At the bottom, and in the layers, the voids in the aggregate structure are almost entirely
filled by the mastic, while, at the surface the voids are only partially filled. It has a rough and
open surface texture. This provides good skidding resistance at all speeds and facilitates the
drainage of surface water (Nunn, 1994).
Stone Matrix Asphalt has excellent deformation and durability characteristics, along with
good fatigue resistance. Stone matrix asphalt has a rough surface texture which offers lower
noise characteristics than dense graded asphalt.
The enhanced deformation resistance, or resistance to rutting, compared to dense graded
asphalt is achieved through mechanical interlock from the high coarse aggregate content forming
a strong stone skeleton. In dense graded asphalt, the lean mastic provides the stability.
The improved durability of SMA comes from its slow rate of deterioration obtained from
the low permeability of the binder rich mastic which cementing the aggregate together.
The increased fatigue resistance is due to higher bitumen content, a thicker bitumen film
over the aggregate and lower air voids content. The higher binder content should also contribute
to flexibility and resistance to reflection cracking from underlying cracked pavements. Fat spots
appear to be the biggest problem.
These are caused by segregation, drain down, and high bitumen content or improper
amount of stabiliser (Brown, et al., 1997). The rich mastic provides good workability and fret
resistance (aggregate retention). The high binder and filler content provide durable, fatigue
resistant, long life bituminous surfacing for heavily trafficked areas.
The difficult task in designing an SMA mix is to ensure a strong stone skeleton with the
correct amount of binder. Too much binder results in pushing the coarse aggregate particles apart,
while too little results in a mix that is difficult to compact. They have high air voids and thin binder
coating and hence less desirable (Wonson, 1998).
In Germany, surface courses of SMA have proven themselves to be exceptionally
resistant to permanent deformation and durable surfaces subject to heavy traffic loads and severe
climatic conditions (DAV, 1992). Stone Matrix Asphalt surface courses are reported to show
excellent results in terms of being particularly stable and durable in traffic areas with maximum
loads and under a variety of weather conditions (Wonson, 1996).

32
The gap-graded aggregate mixture provides a stable stone-to-stone skeleton that is held
together by a rich mixture of bitumen mastic, which is a mixture of bitumen, filler, sand and
stabilizing additives. Stabilizing additives can be organic or mineral fibres, or less often,
polymers. They stabilize the asphalt mortar and tend to thicken or bulk the bitumen to prevent
binder run-off from the aggregate. Thus, they ensure the homogeneity of the mixture. Aggregate
interlock and particle friction are maximized and gives the structure its stability and strength
(Susanne, 2000).
Because the aggregates are all in contact, rut resistance relies on aggregate properties
rather than binder properties. Since aggregates do not deform as much as bitumen binder under
load, this stone-on-stone contact greatly reduces rutting. The improved rutting resistance of the
SMA mixture is attributed to the fact that it carries the load through the coarse aggregate matrix
(or the stone matrix).
The use of polymer or fibre, which increase the viscosity of the mixture, and the use of
high filler content, which increases the stiffness of the binder, allow the SMA mixtures to have a
higher binder film thickness and higher binder content without the problem of drain down of
bitumen during construction. The increased durability of the SMA mixtures can be attributed to
thick film thickness and the high binder content (Chen and Huang, 2008).
Summing up, the properties of a properly designed and constructed SMA can be
enumerated as-
 The stone skeleton, with its high internal friction, will give excellent shear resistance.
 The binder rich, void less mastic will provide good durability and good resistance to
cracking.
 The very high concentration of large stones, three to four times higher than in a
conventional dense graded mixture will give superior resistance to wear.
 The rough surface texture than that of dense graded mixture will assure good skid
resistance and proper light reflection and
 The surface texture also provide anti-splash features during wet and rainy conditions and
 Rduce hydroplaning which results from water draining through the voids in the matrix.

33
CONCLUSION
In recent years there has been a great and continuous effort to utilise EOL tires that are being
stockpiled worldwide. This is primarily due to the issued legislation inside and outside the
European Community, which sets quantitative targets concerning the alternative to landfilling
utilization of such wastes, as well as on technological progress on EOL Tires’ waste
management and the realization of the associated environmental benefits. Main benefit derived
from the utilization of EOL Tires in civil engineering works and especially in road con-
struction is preservation of raw materials and efficient waste management since tire waste either
replaces natural resources or it is utilized as raw material, re-entering construction’s life cycle.
Moreover, in order the measured noise levels to be correlated to an equivalent number of
vehicles at each site, an Equivalent Number of Vehicles (EN) was used, in order to obtain the
actual change in traffic noise level. Results of noise surveys conducted on the rubberized and
conventional pavements, when compared, indicate that the use of rubberized bituminous
mixtures can reduce traffic noise exposure levels by 1 to 3 dB.
This reduction can be attributed to rubber particles structure and characteristics, as well
as in the special mixing conditions for the preparation of the modified binder, which has been
followed in present paper and is unique not only for Greece but for most of the European
countries as well. Moreover, when one considers that the decibel scale is logarithmic every
increase of ten decibels means a sound twice as loud as the former one these numbers
represent significant decreases on traffic noise at the pavement itself.
Advantage of the use of such bituminous mixture has been also certified by citizens and
especially drivers, who mentioned the better performance of the lane, with the modified
rubberised asphalt mixture as far as noise level and comfort in travelling is concerned. The
results of noise reduction could be enhanced if open-graded rubberized bituminous mixture was
implemented, which means by the use of other types of aggregates’ gradations, natural and
recycled ones (derived from Construction and Demolition Wastes-C&D W-), leading to
combined utilization of two waste streams (EOL Tires and C&D W).
The main conclusion of present research, unique for Greece is that rubberized bituminous
mixtures could be a good solution for the re-surfacing of any street which is in poor condition,
since not only does it reduces noise generation, but it also provides more durable pavements
that are less susceptible to the effects of temperature, while maintaining the noise reduction even
after 8 months of operation. Furthermore, the inventory and mapping of road network of Greece
showed that Greece has an existing and projected road network of sufficient length that may be
used for the integration of a huge quantity of EOL Tires providing significant environmental
benefits.

34
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